I had noticed some condensation under my oil fill cap this past week. Didn't really worry about it because I had been doing a lot of short trips and the temp has barely left the single digits outside.

Though after I cleaned the condensation off my oil cap I thought it looked a little too yellow...

What do you think? Is this coolant? I have not noticed any milky oil on the dipstick nor under the oil cap. This stuff looks clear until I wipe it away with a towel. It's not green, but somewhat of a bright yellow. I'm running Royal Purple oil which is purplish/black in color normally.

 

Best anybody can do is guess. A oil sample sent in for analysis will eliminate any guessing (Blackstone Labs I think).

 

I agree that guessing on this is difficult. How many miles on the oil? A nice long highway run might be in order here.........

Unless you have overheated the engine, the 0630 head on your 98 is pretty darn tough.

But for the $20 or so that Blackstone charges, might be money well spent.

 

Ordered a kit from Blackstone. I guess I'll know in a few weeks.

 

There are only a couple hundred miles on this oil change. I overheated it once about 6 months ago, but this is the first I've noticed this yellow stuff. I watch the oil and coolant like a hawk. I lose a bit of coolant, but I have a leak at the water pump/heater core inlet that I'm waiting to fix when it gets warm.

Just had the rear main seal and oil pan gasket replaced, plus put in a new oil pump for the hell of it. Wouldn't think either of those would blow a head gasket/crack head.

 

Any overheat greatly increases the chance for a cracked head or blown head gasket.

Yes, have that oil tested immediately. If coolant is to mix with oil, it doesn't take long to toast engine bearings.

 

Loosing a bit of coolant virtually guarantees air is sucked into the cooling system when the motor cools. Keep very close tabs on coolant level (motor cold) until repairs have been completed.

 

The leak at the water pump is very small. I'm loosing maybe an ounce or two a week. I haven't topped it off in 3 months at the reservoir bottle is still half full at cold (I started with the bottle at full 3 months ago.) I can see the leak though, it's always wet at the front of the valve cover under the inlet and under my thermostat housing.

For air to get sucked in the motor that would mean the reservoir would have to be empty, correct?

 

if you are doing less than 20 minutes of driving then that is just condensation. try a 20 minute or longer drive and most likely it will not be there.
If you had a water into oil leak,,the cap would be the least of your worries
it is normal in the winter time to see it on the cap on short drives.
pull the oil dipstick, if it looks normal then relax and have a beer.

 

What has me worried is the color. It's kind of a bright yellow, maybe it doesn't show up
that bright in the photo. I would think condensation would be more clear.

 

Negative, even a slight leak anywhere in the cooling system will render the coolant recovery system, "the bottle", useless. In order for the coolant recovery system to function correctly, the system must be completely leak free AND the 2 way valve mechanism in the rad cap must function as designed.

 

This is good to know. Hopefully the weather gets warmer soon so I can fix those leaks.